Low noise amplifiers with combined outputs

ABSTRACT

Multiple low noise amplifiers (LNAs) with combined outputs are disclosed. In an exemplary design, an apparatus includes a front-end module and an integrated circuit (IC). The front-end module includes a plurality of LNAs having outputs that are combined. The IC includes receive circuits coupled to the plurality of LNAs via a single interconnection. In an exemplary design, each of the plurality of LNAs may be enabled or disabled via a respective control signal for that LNA. The front-end module may also include receive filters coupled to the plurality of LNAs and a switchplexer coupled to the receive filters. The front-end module may further include at least one power amplifier, and the IC may further include transmit circuits coupled to the at least one power amplifier.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present Application for Patent claims priority to Provisional Application No. 61/524,250, entitled “Method and apparatus for RF front end area and component reduction” filed Aug. 16, 2011, and assigned to the assignee hereof and hereby expressly incorporated by reference herein.

BACKGROUND

I. Field

The present disclosure relates generally to electronics, and more specifically to low noise amplifiers (LNAs).

II. Background

A wireless device (e.g., a cellular phone or a smart phone) in a wireless communication system may transmit and receive data for two-way communication. The wireless device may include a transmitter for data transmission and a receiver for data reception. For data transmission, the transmitter may modulate a radio frequency (RF) carrier signal with data to obtain a modulated RF signal, amplify the modulated RF signal to obtain an output RF signal having the proper output power level, and transmit the output RF signal via an antenna to a base station. For data reception, the receiver may obtain a received RF signal via the antenna and may amplify and process the received RF signal to recover data sent by the base station.

A wireless device may include multiple receivers to support different frequency bands, different radio technologies, receive diversity, etc. It is desirable to implement the receivers to achieve good performance while reducing circuitry and cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless device capable of communicating with different wireless communication systems.

FIG. 2 shows a block diagram of a wireless device.

FIG. 3 shows a receive portion of a wireless device.

FIG. 4 shows a receive portion including LNAs with combined outputs.

FIGS. 5 and 6 show two exemplary designs of single-ended LNAs with combined outputs.

FIG. 8 shows an exemplary design of differential LNAs with combined outputs.

FIG. 9 shows a transceiver including LNAs with combined outputs.

FIG. 10 shows a process for amplifying an input RF signal.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description of exemplary designs of the present disclosure and is not intended to represent the only designs in which the present disclosure can be practiced. The term “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other designs. The detailed description includes specific details for the purpose of providing a thorough understanding of the exemplary designs of the present disclosure. It will be apparent to those skilled in the art that the exemplary designs described herein may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the novelty of the exemplary designs presented herein.

A wireless device comprising multiple LNAs with combined outputs is described herein. Combining the LNA outputs may reduce interconnections, input/output (I/O) ports, circuitry, circuit area, cost, etc., as described below.

FIG. 1 shows a wireless device 110 capable of communicating with different wireless communication systems 120 and 122. Wireless systems 120 and 122 may each be a Code Division Multiple Access (CDMA) system, a Global System for Mobile Communications (GSM) system, a Long Term Evolution (LTE) system, a wireless local area network (WLAN) system, or some other wireless system. A CDMA system may implement Wideband CDMA (WCDMA), cdma2000, or some other version of CDMA. For simplicity, FIG. 1 shows wireless system 120 including one base station 130 and one system controller 140, and wireless system 122 including one base station 132 and one system controller 142. In general, each wireless system may include any number of base stations and any set of network entities.

Wireless device 110 may also be referred to as a user equipment (UE), a mobile station, a terminal, an access terminal, a subscriber unit, a station, etc. Wireless device 110 may be a cellular phone, a smart phone, a tablet, a wireless modem, a personal digital assistant (PDA), a handheld device, a laptop computer, a smartbook, a netbook, a cordless phone, a wireless local loop (WLL) station, a Bluetooth device, etc. Wireless device 110 may be capable of communicating with wireless system 120 and/or 122. Wireless device 110 may also be capable of receiving signals from broadcast stations (e.g., a broadcast station 134). Wireless device 110 may also be capable of receiving signals from satellites (e.g., a satellite 150) in one or more global navigation satellite systems (GNSS). Wireless device 110 may support one or more radio technologies for wireless communication such as LTE, cdma2000, WCDMA, GSM, 802.11, etc.

FIG. 2 shows a block diagram of an exemplary design of wireless device 110 in FIG. 1. In this exemplary design, wireless device 110 includes a transceiver 220 coupled to a primary antenna 210, receivers 230 coupled to a secondary antenna 212, and a data processor/controller 280. Transceiver 220 includes multiple (K) receivers 250 aa to 250 ak and multiple (K) transmitters 270 a to 270 k to support multiple frequency bands, multiple radio technologies, carrier aggregation, etc. Receivers 230 include multiple (M) receivers 250 ba to 250 bm to support multiple frequency bands, multiple radio technologies, receive diversity, multiple-input multiple-output (MIMO) transmission, carrier aggregation, etc.

In the exemplary design shown in FIG. 2, each receiver 250 includes input circuits 252, an LNA 260, and receive circuits 262. For data reception, antenna 210 receives signals from base stations and/or other transmitter stations and provides a received RF signal, which is routed through a switchplexer 240 and provided to a selected receiver. The description below assumes that receiver 250 aa is the selected receiver. Within receiver 250 aa, the received RF signal is passed through input circuits 252 aa and provided to an LNA 260 aa. Input circuits 252 aa may include a receive filter, an impedance matching circuit, a duplexer, etc. LNA 260 aa amplifies the received RF signal from input circuits 252 aa and provides an amplified RF signal. Receive circuits 262 aa amplify, filter, and downconvert the amplified RF signal from RF to baseband and provide an analog input signal to data processor 280. Receive circuits 252 aa may include amplifiers, filters, mixers, impedance matching circuits, an oscillator, a local oscillator (LO) generator, a phase locked loop (PLL), etc. Each remaining receiver 250 in transceiver 220 and each receiver 250 in receivers 230 may operate in similar manner as receiver 250 aa in transceiver 220.

In the exemplary design shown in FIG. 2, each transmitter 270 includes transmit circuits 272, a power amplifier (PA) 274, and output circuits 276. For data transmission, data processor 280 processes (e.g., encodes and modulates) data to be transmitted and provides an analog output signal to a selected transmitter. The description below assumes that transmitter 270 a is the selected transmitter. Within transmitter 270 a, transmit circuits 272 a amplify, filter, and upconvert the analog output signal from baseband to RF and provide a modulated RF signal. Transmit circuits 272 a may include amplifiers, filters, mixers, impedance matching circuits, an oscillator, a LO generator, a PLL, etc. A PA 274 a receives and amplifies the modulated RF signal and provides an amplified signal having the proper output power level. The amplified signal is passed through output circuits 276 a, routed through switchplexer 240, and transmitted via antenna 210. Output circuits 276 a may include a transmit filter, an impedance matching circuit, a directional coupler, a duplexer, etc.

FIG. 2 shows an exemplary design of receivers 250 and transmitters 270. A receiver and a transmitter may also include other circuits not shown in FIG. 2, such as filters, impedance matching circuits, etc. All or a portion of transceiver 220 and receivers 230 may be implemented on one or more analog integrated circuits (ICs), RF ICs (RFICs), mixed-signal ICs, etc. For example, LNAs 260, receive circuits 262, and transmit circuits 272 may be implemented on one module, which may be an RFIC, etc. Switchplexers 240 and 242, input circuits 252, output circuits 276, and PAs 274 may be implemented on another module, which may be a hybrid module, etc. The circuits in receivers 250 and transmitters 270 may also be implemented in other manners.

Data processor/controller 280 may perform various functions for wireless device 110. For example, data processor 280 may perform processing for data being received via receivers 250 and transmitted via transmitters 270. Controller 280 may control the operation of switchplexer 240 and/or 242, input circuits 252, LNAs 260, receive circuits 262, transmit circuits 272, PAs 274, output circuits 276, or a combination thereof. A memory 282 may store program codes and data for data processor/controller 280. Data processor/controller 280 may be implemented on one or more application specific integrated circuits (ASICs) and/or other ICs.

It may be desirable to implement the circuits for receivers on a wireless device in multiple modules. A module is a unit that can include any circuits and further includes I/O ports via which signals can be transmitted and received by the circuits in the module. For example, a module may be an IC die/chip (e.g., an RFIC), an IC package, a hybrid module, a circuit card, etc. A module may comprise a single component such as an IC die/chip. A module may also comprise an assembly of components. For example, a hybrid module may include a circuit board, a housing or an enclosure, and one or more I/O ports (e.g., RF connectors). The circuit board may comprise an alumina substrate or some other substrate and may include passive and/or active devices such as inductors, resistors, discrete transistors, IC dies, etc. As another example, a module may include one or more IC dies mounted on a passive substrate, which may be composed of organic or non-organic material. The passive substrate may include interconnect traces, printed passive circuit components/elements (e.g., inductors), and discrete circuit components (e.g., capacitors, inductors, resistors, etc). A hybrid module may include circuits of one or more technologies, such as discrete field effect transistors (FETs) and/or IC dies attached to a circuit board containing interconnection traces. A front-end module is a module that includes circuits (e.g., switchplexer, filter, duplexer, amplifiers, impedance matching circuits, etc.) located close to an antenna for transmitters and/or receivers. A module may comprise different circuit components but may be treated as a single component. A module may be implemented on a closed or an opened package. Some examples of modules include a front-end module, a power amplifier module (PAM), and a system-in-a-package (SiP) module. A front-end module may be a hybrid module, an IC die, an IC package, etc. Different modules may be implemented in different manners and may be more suitable and economical for different circuits. For example, a hybrid module may be more suitable for filters, impedance matching circuits, micro-electro-mechanical systems (MEMS) switches, etc. An IC die may be more suitable for semiconductor circuits such as amplifiers, semiconductor switches, etc.

A module may be associated with various characteristics. For example, a module may be associated with its own power supply and circuit ground connections. A module may also be treated as a single unit during circuit design and manufacturing.

FIG. 3 shows an exemplary design of a receive portion 300 of a wireless device. In the exemplary design shown in FIG. 3, receive portion 300 includes (i) a front-end module 320 coupled to an antenna 310 and (ii) an RFIC 330 coupled to front-end module 320. Receive portion 300 also include multiple (N) receivers 350 a to 350 n implemented on front-end module 320 and RFIC 330. Receivers 350 a to 350 n may cover N different frequency bands, as shown in FIG. 3. Receivers 350 may also cover different radio technologies, different functions (e.g., carrier aggregation), etc.

In the exemplary design shown in FIG. 3, each receiver 350 includes a receive filter 352, an impedance matching circuit 354, an LNA 360, and receive circuits 362. Receive filter 352 and impedance matching circuit 354 reside in front-end module 320, and LNA 360 and receive circuits 362 reside in RFIC 330. Receive filter 352 and impedance matching circuit 354 may be part of input circuits 252 in FIG. 2. Receive filter 352 filters a received RF signal to pass signal components in a receive frequency band of interest and to attenuate signal components in a transmit frequency band. Impedance matching circuit 354 performs impedance matching between an output impedance of receive filter 352 and an input impedance of LNA 360. LNA 360 amplifies the received RF signal and provides an amplified RF signal. Receive circuits 362 amplify, filter, and downconvert the amplified RF signal from RF to baseband and provide an analog input signal to a data processor (not shown in FIG. 3).

As shown in FIG. 3, multiple receive filters 352, multiple impedance matching circuits 354, multiple LNAs 360, and multiple receive circuits 362 may be used to support multiple frequency bands. Receive filters 352 and impedance matching circuits 354 may be implemented on front-end module 320, which may be a hybrid module. LNAs 360 and receive circuits 362 may be implemented on RFIC 330. Each receiver 350 for a frequency band may then include a receive filter 352 and an impedance matching circuit 354 on front-end module 320 and an LNA 360 and receive circuits 362 on RFIC 330.

The N LNAs 360 a to 360 n in RFIC 330 may be connected to the N impedance matching circuits 354 a to 354 n in front-end module 320 via N interconnections 370 a to 370 n, one interconnection 370 for each LNA 360. Each interconnection 370 is between one I/O port 372 on front-end module 320 and one I/O port 374 in RFIC 330. N I/O ports 372 a to 372 n on front-end module 320 and N I/O ports 374 a to 374 n on RFIC 330 may be used for the N interconnections 370 a to 370 n between front-end module 320 and RFIC 330. There may be many interconnections 370 between front-end module 320 and RFIC 330 if a wireless device supports a number of frequency bands and/or a number of radio technologies. There may also be many I/O ports 372 on front-end module 320 and also many I/O ports 374 on RFIC 330 to support the many interconnections between these two modules.

In an aspect, LNAs with combined outputs may be used in order to reduce the number of interconnections between modules implementing receivers in a wireless device. The LNAs may be implemented on a front-end module and may be coupled directly to receive filters. Receive circuits may be implemented on an RFIC. The outputs of the LNAs may be combined. A single interconnection between the front-end module and the RFIC may then be used for all LNAs whose outputs are combined. Combining the LNA outputs may greatly reduce the number of interconnections between the modules as well as the number of I/O ports on each module. Combining the LNA outputs may also reduce circuitry, circuit area, and cost and may also provide other benefits such as improved performance.

FIG. 4 shows an exemplary design of a receive portion 400 of a wireless device, e.g., wireless device 110 in FIG. 1. In the exemplary design shown in FIG. 4, receive portion 400 includes (i) a front-end module 420 coupled to an antenna 410 and (ii) an RFIC 430 coupled to front-end module 420. Receive portion 400 also include multiple (N) receivers 450 a to 450 n implemented on front-end module 420 and RFIC 430. Receivers 450 a to 450 n may cover N different frequency bands, as shown in FIG. 4. Receivers 450 a to 450 n may also cover different radio technologies, different functions, etc. Receivers 450 a to 450 n may be used for receivers 250 aa to 250 ak for primary antenna 210 in FIG. 2, with N=K . Receivers 450 a to 450 n may also be used for receivers 250 ba to 250 bm for secondary antenna 212 in FIG. 2, with N=M .

In the exemplary design shown in FIG. 4, each receiver 450 includes a receive filter 452, and an LNA 460. The N receivers 450 a to 450 n share receive circuits 462. Receive filter 452 and LNA 360 reside on front-end module 420, and receive circuits 462 reside on RFIC 430. For each receiver 450, receive filter 452 may be part of input circuits 252 in FIG. 2 and may be a surface acoustic wave (SAW) filter or some other type of filter. Receive filter 452 may be (i) a separate receive filter for time division duplexing (TDD) or (ii) part of a duplexer for frequency division duplexing (FDD). Receive filter 452 filters a received RF signal to pass signal components in a receive band and attenuate signal components in a transmit band. In a first exemplary design, receive filter 452 has an output impedance designed to match an input impedance of LNA 460. In a second exemplary design, receive filter 452 has a target output impedance, and impedance matching between receive filter 452 and LNA 460 may not be necessary due to close placement of LNA 460 to receive filter 452. For both the first and second exemplary designs, an impedance matching circuit between receive filter 452 and LNA 460 may be omitted, as shown in FIG. 4. In a third exemplary design, an impedance matching circuit is located between receive filter 452 and LNA 460 and performs impedance matching between the output impedance of receive filter 452 and the input impedance of LNA 460. LNA 460 amplifies the received RF signal and provides an amplified RF signal. Receive circuits 462 amplify, filter, and downconvert the amplified RF signal from RF to baseband and provide an analog input signal to a data processor (e.g., data processor 280 in FIG. 2).

In an exemplary design, receive circuits 462 include common circuits that can be shared by all N receivers 450 a to 450 n. In this exemplary design, the common circuits may have the same biasing for all frequency bands or different biasing for different frequency bands supported by receivers 450 a to 450 n. In another exemplary design, receive circuits 462 include separate circuits for each receiver 450 or each subset of receivers 450 of interest. In this exemplary design, the separate circuits for each receiver 450 or each subset of receivers 450 may be designed to provide good performance for one or more frequency bands supported by that receiver or that subset of receivers.

As shown in FIG. 4, multiple receive filters 452 and multiple LNAs 460 may be used to support multiple frequency bands. Receive filters 452 and LNAs 460 may be implemented on front-end module 420, which may be a hybrid module. Receive circuits 462 may be implemented on RFIC 430. Each receiver 450 for a frequency band may then include a receive filter 452 and an LNA 460 on front-end module 420 and receive circuits 462 on RFIC 330. The N LNAs 360 a to 360 n in RFIC 430 may be connected to receive circuits 462 in front-end module 420 via a single interconnection 470. Interconnection 470 is between an I/O port 472 on front-end module 420 and an I/O port 474 on RFIC 430.

As shown in FIGS. 3 and 4, the number of interconnections between modules as well as the number of I/O ports on each module may be greatly reduced by combining the outputs of LNAs. Furthermore, circuitry may be reduced due to the LNA outputs being combined. In particular, by locating the LNAs on the front-end module instead of the RFIC, impedance matching circuits between the receive filters and the LNAs may be omitted, as shown in FIG. 4. Circuitry may also be reduced by sharing the receive circuits for multiple LNAs, as also shown in FIG. 4.

In an exemplary design, the N LNAs 460 a to 460 n may be individually enabled or disabled via N enable control signals Enbl to EnbN, respectively. One LNA 460 for a selected frequency band may be enabled at any given moment, and remaining LNAs 460 may be disabled. In another exemplary design, multiple LNAs may be simultaneously enabled to amplify a received RF signal and provide an amplified RF signal.

In an exemplary design, N LNAs 460 a to 460 n may be coupled to a common summing node via N switches, which are not shown in FIG. 4. Each LNA 460 may have its output coupled to one end of a switch, and the other end of the switch may be coupled to the common summing node. The switch for each LNA 460 may be opened or closed via a respective enable control signal for that LNA. In another exemplary design, each LNA 460 may be connected to the common summing node when that LNA is enabled or disconnected from the common summing node when the LNA is disabled. Multiple LNAs may also be coupled to a common summing node in other manners.

LNAs with combined outputs may be implemented in various manners. Several exemplary designs of LNAs with combined outputs are described below.

FIG. 5 shows a schematic diagram of an exemplary design of multiple (N) single-ended LNAs 560 a to 560 n with combined outputs. LNAs 560 a to 560 n may be used for LNAs 460 a to 460 n, respectively, in FIG. 4.

Within LNA 560 a, an alternating current (AC) coupling capacitor 574 a has one end receiving an input RF signal (Vin1) for LNA 560 a and the other end coupled to a gate of an N-channel metal oxide semiconductor (NMOS) transistor 570 a. A resistor 576 a has one end receiving a first bias voltage (Vbias1 a) for LNA 560 a and the other end coupled to the gate of NMOS transistor 570 a. NMOS transistor 570 a has its drain coupled to the source of an NMOS transistor 580 a and its source coupled to one end of an inductor 572 a. The other end of inductor 572 a is coupled to circuit ground. NMOS transistor 580 a has its gate receiving a second bias voltage (Vbias1 b) for LNA 560 a and its drain coupled to a summing node A. NMOS transistor 580 a provides an amplified RF signal (Vamp) when LNA 560 a is enabled.

Each of the remaining LNAs 560 b to 560 n may be implemented in similar manner as LNA 560 a. Each LNA 560 x, where index x ∈ {a, . . . , n}, includes NMOS transistors 570 x and 580 x, an inductor 572 x, an AC coupling capacitor 574 x, and a resistor 576 x. For each LNA 560 x, NMOS transistor 570 x receives an input RF signal for that LNA via capacitor 574 x and also receive a first bias voltage for that LNA via resistor 576 x. For each LNA 560 x, NMOS transistor 580 x receives a second bias voltage for that LNA. An inductor 590 is coupled between a power supply voltage (Vdd) and node A. Inductor 590 is a load that is shared by the N LNAs 560 a to 560 n.

Within each LNA 560 x, NMOS transistor 570 x and inductor 572 x form an input gain stage for an input RF signal. NMOS transistor 570 x provide signal amplification for the input RF signal. Inductor 572 x provides source degeneration for NMOS transistor 570 x to improve the linearity of LNAs 560 x. Inductor 572 x may further provide input impedance matching looking into the gate of NMOS transistor 570 x. NMOS transistor 580 x is a cascode transistor that provides load isolation for NMOS transistor 570 x and also provides signal drive for an amplified RF signal from LNA 560 x. LNA 560 x may be enabled or disabled based on the first bias voltage for NMOS transistor 570 x and/or the second bias voltage for NMOS transistor 580 x. The bias voltages for each LNA 560 x may be generated based on an enable control signal for that LNA.

N different input RF signals Vin1 to VinN are provided to N LNAs 560 a to 560 n, respectively. The input RF signals for LNA 560 a to 560 n may be provided by N receive filters, e.g., receive filters 452 a to 452 n in FIG. 4. N first bias voltages Vbias1 a to VbiasNa and N second bias voltages Vbias1 b to VbiasNb are also provided to N LNAs 560 a to 560 n.

FIG. 6 shows a schematic diagram of an exemplary design of multiple (N) single-ended LNAs 660 a to 660 n with combined outputs. LNAs 660 a to 660 n may also be used for LNAs 460 a to 460 n, respectively, in FIG. 4.

Each LNA 660 x, where index x ∈ {a, . . . , n}, includes an NMOS transistors 670 x, a source degeneration inductor 672 x, an AC coupling capacitor 674 x, and a resistor 676 x, which are coupled in the same manner as NMOS transistor 570 a, inductor 572 a, capacitor 574 a, and resistor 576 x in LNA 560 a in FIG. 5. The drains of NMOS transistors 670 a to 670 n for the N LNAs 660 a to 660 n are coupled to a summing node B. An NMOS transistor 680 has its source coupled to summing node B, its gate receiving a bias voltage (Vbias0), and its drain providing an amplified RF signal (Vamp). An inductor 690 has one end coupled to the drain of NMOS transistor 680 and the other end coupled to the Vdd voltage.

For each LNA 660 x, NMOS transistor 670 x receives an input RF signal (Vin) for that LNA via capacitor 674 x and also receive a bias voltage (Vbias) for that LNA via resistor 676 x. N different input RF signals Vin1 to VinN are provided to N LNAs 660 a to 660 n, respectively. N bias voltages Vbias1 to VbiasN are also provided to N LNAs 660 a to 660 n, respectively.

Within each LNA 660 x, NMOS transistor 670 x and inductor 672 x form an input gain stage. Each LNA 660 x may be enabled or disabled based on the bias voltage for that LNA, which may be generated based on an enable control signal for that LNA. NMOS transistor 680 is a common cascode transistor for all N LNAs 660 a to 660 n. Inductor 690 is a common load inductor for all N LNAs 660 a to 660 n.

FIG. 7 shows a schematic diagram of an exemplary design of multiple (N) single-ended LNAs 760 a to 760 n with combined outputs. LNAs 760 a to 760 n may also be used for LNAs 460 a to 460 n, respectively, in FIG. 4. LNAs 760 a to 760 n are implemented on a front-end module 730 and are coupled to receive circuits 762 on an RFIC 730 via a single interconnection 722.

Each LNA 760 x, where index x ∈ {a, . . . , n} , includes an NMOS transistors 770 x and a source degeneration inductor 772 x, which are coupled in the same manner as NMOS transistor 570 a and inductor 572 a in LNA 560 a in FIG. 5. Each LNA 760 x also includes an input impedance matching circuit 764 x comprising (i) a shunt circuit component 766 x coupled between the input of LNA 760 x and circuit ground and (ii) a series circuit component 768 x coupled between the input of LNA 760 x and the gate of NMOS transistor 770 x. Circuit components 764 x and 766 x may each be an inductor or a capacitor. The drains of NMOS transistors 770 a to 770 n for LNAs 760 a to 760 n, respectively, are coupled to a summing node D. A transmission line 776 is coupled between summing node D and an I/O port 778 on front-end module 720.

For each LNA 760 x, NMOS transistor 770 x receives an input RF signal (Vin) for that LNA. N different input RF signals Vin1 to VinN are provided to N LNAs 760 a to 760 n, respectively. Each LNA 760 x may be enabled or disabled based on the bias voltage for that LNA (not shown in FIG. 7). The N LNAs 760 a to 760 n on front-end module 720 have a current mode interface to receive circuits 762 on RFIC 730.

Receive circuits 762 include a common gate stage 780, a bypassable amplifier 790, an AC coupling capacitor 748, and a mixer 750. Amplifier 790 includes NMOS transistors 792 and 794, a source degeneration inductor 796, and a load inductor 798, which are coupled in similar manner as NMOS transistors 570 a and 580 a and inductor 572 a and 590 in FIG. 5. Load inductor 798 may be replaced with an active load composed of one or more MOS transistors. Common gate stage 780 includes NMOS transistors 782 and 784 and an AC coupling capacitor 786. NMOS transistor 782 has its source coupled to circuit ground, its gate receiving a first bias voltage (Vbias1), and its drain coupled to the gate of NMOS transistor 792. NMOS transistor 784 has its source coupled to the input of receive circuits 762, its gate receiving a second bias voltage (Vbias2), and its drain coupled to the drain of NMOS transistor 792. Capacitor 786 is coupled between the input of receive circuits 762 and the gate of NMOS transistor 792. In general, a common gate stage includes a transistor (e.g., NMOS transistor 784) having its gate coupled to AC ground, its source receiving an input signal, and its drain providing an output signal.

Common gate stage 780 on RFIC 730 supplies bias current to LNAs 760 a to 760 n on front-end module 720. Amplifier 790 may be bypassed by turning off NMOS transistor 792 via NMOS transistor 782. In particular, NMOS transistor 792 may be turned off by pulling its gate to a low voltage (e.g., to 0 Volts), which may be achieved by applying a high bias voltage at the gate of NMOS transistor 782. NMOS transistor 784 may be turned on and may operate as switch. As a result, the bias current of NMOS transistor 794 may be routed to NMOS transistor 770 in a selected/enabled LNA 760. An output signal from NMOS transistor 770 in the selected LNA 760 may be routed via NMOS transistor 784 to NMOS transistor 794. A cascode amplifier may be formed by NMOS transistors 770 and 794 (instead of NMOS transistors 792 and 794). Impedance matching to transmission line 776 may be achieved via the input impedance of common gate stage 780 and the ON resistance of NMOS transistor 784, which operates as a switch.

The exemplary design in FIG. 7 may provide various advantages. First, LNAs 760 may be implemented in a smaller circuit area since a load inductor may be omitted. Second, mixer 750 may be isolated from front-end module 720 via common gate stage 780. Third, LNAs 760 a to 760 n are implemented with a common source circuit design and have good noise figure. Fourth, the circuit design in FIG. 7 may allow for easier implementation of bypassable amplifier 790 on RFIC 730.

FIG. 8 shows a schematic diagram of an exemplary design of multiple (N) differential LNAs 860 a to 860 n with combined outputs. LNAs 860 a to 860 n may also be used for LNAs 460 a to 460 n, respectively, in FIG. 4.

LNA 860 a includes NMOS transistors 870 a and 880 a, an inductor 872 a, a capacitor 874 a, and a resistor 876 a that are coupled in the same manner as NMOS transistors 570 a and 580 a, inductor 572 a, capacitor 574 a, and resistor 576 a in FIG. 5. LNA 860 a also includes NMOS transistors 870 b and 880 b, an inductor 872 b, a capacitor 874 b, and a resistor 876 b that are also coupled in the same manner as NMOS transistors 570 a and 580 a, inductor 572 a, capacitor 574 a, and resistor 576 a in FIG. 5. LNA 860 a receives a differential input RF signal composed of a Vin1 p signal and a Vin1 n signal. The Vin1 p signal is provided to capacitor 874 a, and the Vin1 n signal is provided to capacitor 874 b. The drain of NMOS transistor 880 a is coupled to a first summing node E, and the drain of NMOS transistor 880 b is coupled to a second summing node F. An inductor 890 a is coupled between node E and the Vdd voltage. An inductor 890 b is coupled between node F and the Vdd voltage.

Each of the remaining LNAs 860 b to 860 n may be implemented in similar manner as LNA 860 a. N differential input RF signals are provided to N LNAs 860 a to 860 n. Each differential input RF signal includes (i) a non-inverting input RF signal (e.g., Vin1 p) provided to a first NMOS transistor in an associated LNA 860 and (ii) an inverting input RF signal (e.g., Vin1 n) provided to a second NMOS transistor in the associated LNA 860. A differential amplified RF signal composed of a Vampp signal and a Vampn signal is provided via nodes E and F.

Differential LNAs 860 a to 860 n in FIG. 8 are based on single-ended LNAs 560 a to 560 n in FIG. 5. Differential LNAs may also be implemented based on single-ended LNAs 660 a to 660 n in FIG. 6.

FIGS. 5 to 8 show three exemplary designs of LNAs with combined outputs.

LNAs with combined outputs may also be implemented in other manners. For example, a gain transistor may be implemented with multiple NMOS transistors coupled in parallel. A load inductor may be replaced with an active load, which may be implemented with P-channel metal oxide semiconductor (PMOS) transistors or some other type of transistors.

LNAs 560 a to 560 n in FIG. 5, LNAs 660 a to 660 n in FIG. 6, and LNAs 860 a to 860 n in FIG. 8 may be designed to provide good performance for their associated frequency bands. For example, the size of the NMOS transistors, the bias voltage and/or the bias current for the NMOS transistors, the value of the source degeneration inductor, and/or other characteristics of each LNA may be designed to provide good performance at the frequency band supported by that LNA. Different LNAs may have different transistor sizes, differential biasing (e.g., different bias voltages and/or different bias currents), different source inductances, etc.

Although not shown in FIGS. 5 to 8, a capacitor may be coupled in parallel with a load inductor, e.g., inductor 590 in FIG. 5, inductor 690 in FIG. 6, or each of inductors 890 a and 890 b in FIG. 8. The load inductor and the capacitor would form a resonator circuit having a resonant frequency. The capacitor may be adjustable/variable, and the resonant frequency may be adjusted by varying the capacitance of the capacitor. The resonant frequency may be set to a frequency band of interest. An adjustable capacitor may enable load tuning across different frequency bands supported by the N LNAs sharing the load inductor.

A wireless device may require a complex RF front-end due to proliferation of frequency bands and operating modes. Conventionally, PAs, duplexers, filters, and switches are implemented with discrete components. LNAs are typically located in a transceiver (e.g., an RFIC), and PAs are typically stand-alone. LNAs and PAs are typically separated from their associated filters and duplexers. Hence, many RF routing traces and impedance matching components are typically required between the filters and/or duplexers and their associated LNAs and PAs. Large board area is typically consumed by discrete PAs, discrete filters and/or duplexers, and interconnections between the filters and/or duplexers and their associated LNAs and PAs.

In another aspect, a more compact wireless device may be achieved by combining LNAs, PAs, duplexers, filters, and switches in one or more modules. LNAs and PAs may be monolithically integrated on the same IC die or may be implemented on different IC dies in the same package. Switches may be monolithically integrated with the LNAs and/or PAs or may be implemented on different IC dies in the same package. Combining LNAs, PAs, duplexers, filters, and switches may reduce interconnections, avoid impedance matching components, reduce board area, and possibly provide other benefits.

FIG. 9 shows an exemplary design of a transceiver 900 for a wireless device. In the exemplary design shown in FIG. 9, transceiver 900 includes (i) a front-end module 920 coupled to an antenna 910 and (ii) an RFIC 930 coupled to front-end module 920. Transceiver 900 also includes (i) L receivers and L transmitters for low band and (ii) H receivers and H transmitters for high band, all of which are implemented on front-end module 920 and RFIC 930, where L and H may each be any integer value. The L receivers for low band may cover different frequency bands and/or different radio technologies for low band. The H receivers for high band may cover different frequency bands and/or different radio technologies for high band.

In the exemplary design shown in FIG. 9, each receiver for low band includes a duplexer 952, an LNA 960, and receive circuits 962. In the receiver for low band 1, a duplexer 952 aa has its output port coupled to one end of a switch 942 aa within a switchplexer 940 and its receive port coupled to the input of an LNA 960 aa. Each remaining receiver for low band is connected in similar manner as the receiver for low band 1. The outputs of the L LNAs 960 aa to 960 al for low band are connected together and coupled via an interconnection 968 a to receive circuits 962 a on RFIC 930. Each receiver for high band is connected in similar manner as each receiver for low band. The outputs of the H LNAs 960 ba to 960 bh for high band are connected together and coupled via an interconnection 968 b to receive circuits 962 b on RFIC 930.

In the exemplary design shown in FIG. 9, each transmitter for low band includes transmit circuits 972, a PA 974, and duplexer 952. In the transmitter for low band 1, a PA 974 a has its input connected via an interconnection 978 a to transmit circuits 962 a on RFIC 930. PA 974 aa has its output connected to a transmit port of duplexer 952 aa via a switch 976 aa. Each remaining transmitter for low band is connected in similar manner as the transmitter for low band 1. Each transmitter for high band is also connected in similar manner as each transmitter for low band. The input of a PA 974 b for high band is coupled via an interconnection 978 b to transmit circuits 972 b on RFIC 930.

As shown in FIG. 9, the number of RF connections between front-end module 920 and RFIC 930 as well as the number of I/O ports on each of front-end module 920 and RFIC 930 may be substantially reduced by combining the outputs of LNAs. Combining the LNA outputs may be especially advantageous when there are many LNAs for many frequency bands and/or many radio technologies. Furthermore, impedance matching circuits between duplexers 952 and LNAs 960 may be omitted by placing the LNAs close to the duplexers.

FIG. 9 shows an exemplary design of transceiver 900 for FDD. In this case, a duplexer 952 is shared by a receiver and a transmitter. A duplexer includes a transmit filter and a receive filter integrated on one package. For TDD, a PA may be coupled directly to a switchplexer without going through a duplexer, and an LNA may be coupled to a receive filter instead of a duplexer.

The exemplary design in FIG. 9 shows various features of the present disclosure. First, the outputs of multiple LNAs on one module may be combined and coupled via a single interconnection to receive circuits on another module. Alternatively, the inputs of multiple LNAs may also be combined, and the outputs of the LNAs may be coupled via switches to a single interconnection. Second, a front-end module may include LNAs with combined outputs as well as one or more PAs, one or more receive filters, one or more transmit filters, one or more duplexers, or a combination thereof. A PA may support multiple frequency bands and/or multiple modes of operation and may be coupled to switches to select a particular frequency band and/or a particular mode, as shown in FIG. 9. A PA may have its input coupled to common transmit circuits for multiple frequency bands and/or multiple modes and may have its output coupled to multiple transmit paths (e.g., duplexers) for different frequency bands and/or different modes. p FIGS. 4 and 9 show two exemplary designs of a front-end module with multiple sets of LNAs and receive filters/duplexers, where the LNA outputs are combined at a common load. This allows multiple sets of LNAs and receive filters/duplexers to be connected to a single interconnection. The LNAs may be coupled directly to the receive filters/duplexers without going through impedance matching circuits, as shown in FIGS. 4 and 9. The LNAs with combined outputs may be used for primary receivers coupled to a primary antenna as well as for secondary receivers (e.g., diversity receivers) coupled to a secondary antenna.

In an exemplary design, an apparatus (e.g., a wireless device, an IC, a circuit module, etc.) may comprise a front-end module and an IC. The front-end module (e.g., front-end module 420 in FIG. 4) may comprise a plurality of LNAs (e.g., LNAs 460 a to 460 n in FIG. 4) having outputs that are combined. The IC (e.g., RFIC 430 in FIG. 4) may comprise receive circuits (e.g., receive circuits 462) coupled to the plurality of LNAs via a single interconnection (e.g., interconnection 470 in FIG. 4). In an exemplary design, the front-end module may comprise a hybrid module including circuit components of different technologies. In an exemplary design, the IC may comprise an RFIC. The front-end module and the IC may also comprise modules of other types. The single interconnection may be associated with a single I/O port on the front-end module, a single I/O port on the IC for a single-ended design, and a single RF routing trace between these I/O ports, e.g., as shown in FIG. 5. Alternatively, the single interconnection may be associated with two I/O ports on the front-end module, two I/O ports on the IC, and two RF routing traces between the two I/O ports on the front-end module and the two I/O ports on the IC for a differential LNA design.

In an exemplary design, each of the plurality of LNAs may be enabled for disabled via a respective control signal for that LNA, e.g., as shown in FIG. 4. A subset (e.g., one) of the plurality of LNAs may be enabled at any given moment, and remaining ones of the plurality of LNAs may be disabled.

In an exemplary design, the front-end module may comprise at least one receive filter (e.g., filters 452 a to 452 n in FIG. 4) coupled to at least one of the plurality of LNAs. At least one of the plurality of LNAs may be coupled directly to the at least one receive filter, without going through an impedance matching circuit, as shown in FIG. 4. The at least one receive filter may be part of at least one duplexer, e.g., as shown in FIG. 9. The front-end module may further comprise a switchplexer (e.g., switchplexer 440 in FIG. 4) coupled to the at least one receive filter. The front-end module may also comprise other circuit components.

In an exemplary design, each of the plurality of LNAs may comprise a first transistor and a second transistor, e.g., as shown in FIG. 5. The first transistor (e.g., NMOS transistor 570 a in FIG. 5) may have a gate receiving an input RF signal. The second transistor (e.g., NMOS transistor 580 a in FIG. 5) may have a drain coupled to a summing node (e.g., node A in FIG. 5) and a source coupled to a drain of the first transistor.

In another exemplary design, each of the plurality of LNAs may comprise a first transistor (e.g., NMOS transistor 670 a in FIG. 6 or NMOS transistor 760 a in FIG. 7) having a gate receiving an input RF signal and a drain coupled to a summing node (e.g., node B in FIG. 6 or node D in FIG. 7). In an exemplary design, the plurality of LNAs may further comprise a second transistor (e.g., NMOS transistor 680 in FIG. 6) having a source coupled to the summing node and a drain providing an amplified RF signal. In another exemplary design, the summing node may be coupled via a current interface to the receive circuits, e.g., as shown in FIG. 7. The receive circuits may comprise a common gate stage and an amplifier. The common gate stage (e.g., common gate stage 780 in FIG. 7) may provide bias current for the plurality of LNAs. The amplifier (e.g., amplifier 790 in FIG. 7) may be coupled to the common gate stage and may be bypassable via the common gate stage.

In one exemplary design, each LNA may be a single-ended LNA receiving a single-ended input RF signal and providing a single-ended amplified RF signal, e.g., as shown in FIGS. 5 and 6. In another exemplary design, each LNA may be a differential LNA receiving a differential input RF signal and providing a differential amplified RF signal, e.g., as shown in FIG. 8.

In an exemplary design, the plurality of LNAs may comprise a load inductor (e.g., inductor 590 in FIG. 5) shared by the plurality of LNAs. The plurality of LNAs may further comprise an adjustable capacitor coupled in parallel with the load inductor. The plurality of LNAs may be associated with different transistor sizes, different transistor biasing, different LNA circuit designs, some other different characteristics, or a combination thereof

In an exemplary design, the plurality of LNAs (e.g., LNAs 960 aa to 960 al in FIG. 9) may be for low band. The front-end module may further comprise a second plurality of LNAs (e.g., LNAs 960 ba to 960 bh in FIG. 9) for high band and having outputs that are combined. The IC may further comprise second receive circuits (e.g., receive circuits 962 b) coupled to the second plurality of LNAs via a second interconnection.

In an exemplary design, the front-end module may further comprise at least one power amplifier (e.g., PA 974 a and/or 974 b in FIG. 9). The IC may further comprise transmit circuits (e.g., transmit circuits 972 a and/or 972 b in FIG. 9) coupled to the at least one power amplifier. The front-end module may further comprise a plurality of transmit filters or a plurality of duplexers for a plurality of frequency bands, e.g., as shown in FIG. 9. The at least one power amplifier may include a power amplifier supporting the plurality of frequency bands and coupled to the plurality of transmit filters or the plurality of duplexers via a plurality of switches, e.g., as shown in FIG. 9.

FIG. 10 shows an exemplary design of a process 1000 for performing signal amplification. A received RF signal may be filtered with one of at least one filter to obtain an input RF signal (block 1012). The at least one filter may be coupled to at least one of a plurality of LNAs. The input RF signal may be amplified with a selected LNA among the plurality of LNAs having outputs that are combined and residing on a front-end module (block 1014). An amplified RF signal from the selected LNA may be received by receive circuits residing on an IC via a single interconnection coupling the plurality of LNAs to the receive circuits (block 1016). The receive circuits may process the amplified RF signal and provide an analog input signal.

An analog output signal may be conditioned (e.g., amplified, filtered, upconverted, etc.) by transmit circuits residing on the IC to obtain an output RF signal (block 1018). The output RF signal may be amplified with a selected power amplifier among at least one power amplifier residing on the front-end module (block 1020).

Multiple LNAs with combined outputs, as described herein, may be implemented on an IC, an analog IC, an RFIC, a mixed-signal IC, an ASIC, a printed circuit board (PCB), an electronic device, etc. Multiple LNAs with combined outputs may be fabricated with various IC process technologies such as complementary metal oxide semiconductor (CMOS), NMOS, PMOS, bipolar junction transistor (BJT), bipolar-CMOS (BiCMOS), silicon germanium (SiGe), gallium arsenide (GaAs), heterojunction bipolar transistors (HBTs), high electron mobility transistors (HEMTs), silicon-on-insulator (SOI), etc.

An apparatus implementing multiple LNAs with combined outputs, as described herein, may be a stand-alone device or may be part of a larger device. A device may be (i) a stand-alone IC, (ii) a set of one or more ICs that may include memory ICs for storing data and/or instructions, (iii) an RFIC such as an RF receiver (RFR) or an RF transmitter/receiver (RTR), (iv) an ASIC such as a mobile station modem (MSM), (v) a module that may be embedded within other devices, (vi) a receiver, cellular phone, wireless device, handset, or mobile unit, (vii) etc.

In one or more exemplary designs, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. 

1. An apparatus comprising: a front-end module comprising a plurality of low noise amplifiers (LNAs) having outputs that are combined; and an integrated circuit (IC) comprising receive circuits coupled to the plurality of LNAs via a single interconnection.
 2. The apparatus of claim 1, the front-end module further comprising at least one power amplifier, and the IC further comprising transmit circuits coupled to the at least one power amplifier.
 3. The apparatus of claim 2, the front-end module further comprising a plurality of transmit filters or a plurality of duplexers for a plurality of frequency bands, and the at least one power amplifier comprising a power amplifier supporting the plurality of frequency bands and coupled to the plurality of transmit filters or the plurality of duplexers.
 4. The apparatus of claim 1, wherein a subset of the plurality of LNAs is enabled at any given moment and remaining ones of the plurality of LNAs are disabled.
 5. The apparatus of claim 1, the front-end module comprising: at least one receive filter coupled to at least one of the plurality of LNAs.
 6. The apparatus of claim 1, each of the plurality of LNAs comprising: a first transistor having a gate receiving an input radio frequency (RF) signal; and a second transistor having a drain coupled to a summing node and a source coupled to a drain of the first transistor.
 7. The apparatus of claim 1, each of the plurality of LNAs comprising: a first transistor having a gate receiving an input radio frequency (RF) signal and a drain coupled to a summing node.
 8. The apparatus of claim 7, the plurality of LNAs comprising: a second transistor having a source coupled to the summing node and a drain providing an amplified RF signal.
 9. The apparatus of claim 7, the receive circuits comprising: a common gate stage configured to provide bias current for the plurality of LNAs; and an amplifier coupled to the common gate stage.
 10. The apparatus of claim 1, each of the plurality of LNAs comprising: a single-ended LNA receiving a single-ended input radio frequency (RF) signal and providing a single-ended amplified RF signal.
 11. The apparatus of claim 1, each of the plurality of LNAs comprising: a differential LNA receiving a differential input radio frequency (RF) signal and providing a differential amplified RF signal.
 12. The apparatus of claim 1, the plurality of LNAs comprising: a load inductor shared by the plurality of LNAs.
 13. The apparatus of claim 12, the plurality of LNAs further comprising: an adjustable capacitor coupled in parallel with the load inductor.
 14. The apparatus of claim 1, wherein the plurality of LNAs are associated with at least one of different transistor sizes, different transistor biasing, or different LNA circuit designs.
 15. The apparatus of claim 1, the plurality of LNAs are for low band, the front-end module further comprising a second plurality of LNAs for high band and having outputs that are combined, and the IC further comprising second receive circuits coupled to the second plurality of LNAs via a second interconnection.
 16. A method comprising: amplifying an input radio frequency (RF) signal with a selected low noise amplifier (LNA) among a plurality of LNAs having outputs that are combined and residing on a front-end module; and receiving, at receive circuits residing on an integrated circuit (IC), an amplified RF signal from the selected LNA via a single interconnection coupling the plurality of LNAs to the receive circuits.
 17. The method of claim 16, further comprising: filtering a received RF signal with one of at least one filter to obtain the input RF signal, the at least one filter being coupled to at least one of the plurality of LNAs.
 18. The method of claim 16, further comprising: conditioning, with transmit circuits residing on the IC, an analog output signal to obtain an output RF signal; and amplifying the output RF signal with a selected power amplifier among at least one power amplifier residing on the front-end module.
 19. An apparatus comprising: a plurality of means for amplifying having outputs that are combined and residing on a first module, one of the plurality of means for amplifying being selected to amplify an input radio frequency (RF) signal and provide an amplified RF signal; and means for processing the amplified RF signal, the means for processing residing on a second module and being coupled to the plurality of means for amplifying via a single interconnection.
 20. The apparatus of claim 19, further comprising: means for filtering a received RF signal to obtain the input RF signal, the means for filtering being coupled to the selected one of the plurality of means for amplifying. 